Modern pneumatic tires, especially tubeless tires, are usually mounted on wheels with rims that capture the tire bead to ensure maintenance of the desired airtight seal between the tire and the wheel rim. In order to break the seal between the tire bead and the rim, it is usual to use a power operated bead breaker capable of exerting sufficient force on the tire side wall to dislodge the bead from the rim. In many cases, however, a tire will need repairs in a field situation far from the nearest power operated tire changing equipment. For example, where a tire on a farm truck or a tractor fails in the field, removing the wheel to the nearest tire repair equipment causes considerable non-productive down time. To solve this problem, various manually operated devices have been proposed to permit the ready removal of tires from rims. These include the devices disclosed in the following:
U.S. Pat. No. 2,684,710 to Calvin describes a tool which is fastened to a wheel using a hook that engages the center hub opening of the wheel and a hook shaped head that engages the wheel rim. The device is tightened in place using a nut threaded onto the shank of the hob hook. A pusher head slides in a socket in the head and is driven against the tire side wall with a bolt in order to dislodge the tire bead from the rim. The mounting system used in this device does not provide a positive securement of the device to the wheel rim where the bead is to be broken. Over tightening of the hub engaging hook may well bend the wheel, especially in the critical rim area.
U.S. Pat. No. 4,785,865 to Folstad describes a device that has a screw operated clamp that is intended to clamp directly onto the rim where the bead is to be broken. The very large forces required to unseat the tire bead will tend to rotate this tool around the rim, applying a bending moment to the rim.
U.S. Pat. No. 3,707,179 to LePier discloses another tool with a screw operated clamp that clamps directly onto the rim of the wheel.
U.S. Pat. No. 3,253,640 to Paulauskas discloses a device that clamps onto a wheel rim to provide a moveable fulcrum for a tire iron.
U.S. Pat. No. 3,648,751 to Archidoit discloses a device that clamps onto the rim and has a backup wing head bolt engaging the wheel centre flange to resist movements from the pusher head. This device is power operated.
U.S. Pat. No. 4,850,413 to Blank describes a bead breaker in which a tire iron and a rim hook are two parallel plates that are pivotally connected at a position spaced outwardly from the tire tread.